1. Field of Invention
The present invention relates to aircraft, and particularly to vertical takeoff and landing (VTOL) aircraft.
2. Cross Reference to Related Documentation
USPTO Disclosure Document No. 492789, filed Apr. 26, 2001
Inventor: Brad C Hansen
Title: Circular Wing Vertical Takeoff and Landing Aircraft
3. Technical Background
Atmospheric flying machines (aircraft) fall into three general categories. The first category, fixed-wing, depends upon horizontal motion of the aircraft to generate vertical lift forces on the wing as the result of airflow over the wing. Lifting forces are generated due to the camber shape of the wing which causes the air flowing above the wing to move faster than the air below the wing, thus resulting in low pressure above the wing relative to that below the wing. Vertical forces are also generated on fixed wing aircraft at high horizontal speeds when the pitch angle of the wing relative to the horizontal wind is positive, exposing an increased surface area of the wing to the wind. The force of the air molecules hitting against the angled wing surface results in both horizontal (drag) and vertical (lift) forces on the wing. Since this type of aircraft requires horizontal motion before achieving vertical lift, ground runways are required.
The second general category of aircraft, vertical takeoff and landing, may generate vertical lift forces without initial horizontal motion by rotating unfixed wings or wing-like blades above or about the aircraft. Helicopters fall into this category. Another type of aircraft in this category simply generates large vertical thrust forces great enough to overcome the weight of the aircraft. The British Harrier falls into this category. Since horizontal motion of the aircraft is not needed to generate lift, this second category of aircraft does not require a runway.
A third general category of aircraft, the airship, uses the buoyancy of a contained gas that is lighter than surrounding atmospheric gases. When lifting force of buoyancy exceeds the weight of the container and anything attached to it, the airship rises. Hot air balloons and dirigibles fall into this category.
Each of these three categories of aircraft have advantages and drawbacks. Fixed-wing aircraft are better for long range flights because they can be aerodynamically designed for faster speeds, thus reducing travel time, and they are more efficient (cost/mile) than VTOL aircraft. But because of the need for a runway, fixed-wing aircraft become less practical as the distance traveled gets shorter, such as for local transportation. Existing VTOL aircraft, although better for short flights, are too expensive to operate, not only due to flight inefficiency but also because they are very mechanically complex and therefore are costly to build and maintain. This level of complexity, and tendency to break, leads to safety concerns when applied to its most useful application—short local flights over typically populated areas. Although efficient, airships are very slow and difficult to control, especially in high wind conditions.
What is needed for short local and regional flights is a revolutionary new type of VTOL aircraft that does not have the drawbacks of current VTOL aircraft. A VTOL aircraft is needed that is very efficient to operate and mechanically simple, thus reducing operating costs and recurring maintenance costs, and greatly reducing safety concerns.